of habitats, mean levels of polymorphism and mean genetic distances for each habitat were calculated (Table 7). When all populations from all geographic re-gions and habitats were compared, the highest levels of intrapopulational diversity were observed within the alpine rocky ridge populations, followed by calcareous grasslands, beechforests and lowland rocky ridges. The lowest level of intrapopu-lational variation was observed on the rocky river valley slopes and in the fens.
Sesleria albicans – Results
Table 7: Genetic variation within the populations of Sesleria albicans in different habi-tats (Rocky river valley slopes, lowland rocky ridges, calcareous grasslands, beechforests, fens and alpine rocky ridges) from different geographic regions. For each habitat mean percentage of polymorphic bands and mean genetic distances were calculated.
Habitat Fen Rocky river
valley slope
Lowland rocky ridge
Beech-forest
Calcareous grassland
Alpine rocky ridge Populations from all geographic regions:
Polymorphic bands (%) 42,3 43,6 48,2 48,3 52,4 55,9 Jaccard-Dist. Min (%) 18,2 18,8 24,4 25,3 28,6 30,8 Jaccard-Dist. Max (%) 29,7 31,2 35,5 34,5 36,6 39,1 Jaccard-Dist. Mean (%) 26,2 26,3 30,1 30,3 33,1 35,6 S. of euc. Squares/n-1 22,0 22,3 26,3 25,8 28,1 29,1
Populations from southwest Germany only:
Polymorphic bands (%) 42,3 46.6 48.2 48.4 52.8 - Jaccard-Dist. Min (%) 18,2 25.5 24.4 24.6 26.8 - Jaccard-Dist. Max (%) 29,7 31.7 35.5 35.1 37.2 - Jaccard-Dist. Mean (%) 26,2 28.7 30.1 30.3 33.2 - S. of euc. Squares/n-1 22,0 24,4 26,3 25,7 27,5 -
Populations from west Germany only:
Polymorphic bands (%) - 41.6 - 48.1 51.9 - Jaccard-Dist. Min (%) - 14.4 - 26.3 30.4 - Jaccard-Dist. Max (%) - 30.9 - 33.6 35.9 - Jaccard-Dist. Mean (%) - 24.6 - 30.3 33.1 - S. of euc. Squares/n-1 - 21,0 - 26,0 28,7 -
The same pattern was observed, when comparing populations from different habi-tats in southwest or west Germany only. In southwest Germany the lowest level of intrapopulational diversity was found in the fens and on the rocky river valley slopes, whereas the highest diversity was observed in the calcareous grasslands.
The west German populations also showed lower levels of variation on the rocky river valley slopes and higher levels of diversity in the calcareous grasslands.
The results were different, when comparing intrapopulational diversity of all populations from the Alps with all populations from southwest Germany and west Germany (Table 8). In this case approximately as much variation was found within the southwest German as within the west German populations. However, the alpine populations showed higher variation than the lowland populations.
Table 8: Genetic variation within the populations of Sesleria albicans from West and Central Germany, from Southwest Germany and the Alps. For each geographic region mean percentage of polymorphic bands and mean genetic distances were calculated.
Region West and Central Germany Southwest Germany Alps
Polymorphic bands (%) 47.1 47.3 55.9
Jaccard-Distance Min (%) 23.4 23.4 30.8 Jaccard-Distance Max (%) 33.5 33.7 39.1 Jaccard-Distance Mean (%) 29.2 29.5 35.6 Sums of euclidian squares/n-1 25.1 25.0 29.0
3.6 Molecular variance and population size
The S. albicans population sizes ranged from 20,000 to just a few square meters (Table 1). The level of polymorphism correlated highly significant with the popu-lation size (Spearman’s rank-correpopu-lation coefficient rs=0.7, P<0.001, Figure 4a). A highly significant correlation was also observed between population size and the minimum and mean genetic distance, taken from the Jaccard’s similarity index matrix (rs=0.7, P<0.001, Figure 4b).
r = 0.7 P<0.001
0,00 10,00 20,00 30,00 40,00 50,00 60,00
0 0,5 1 1,5 2 2,5 3 3,5 4 4,5 5
Log populations size
Polymorphic bands (%)
Figure 4a: Correlation between population size and the percentage of polymor-phic bands per population, calculated for Sesleria albicans.
Sesleria albicans – Results
r = 0.7 P<0.001
0 5 10 15 20 25 30 35 40
0 0,5 1 1,5 2 2,5 3 3,5 4 4,5 5
Log population size
Mean genetic distance (%)
Figure 4b: Correlation between population size and mean genetic distance per popula-tion, calculated for Sesleria albicans.
r = 0.7 P<0.001
0 5 10 15 20 25 30 35
0 0,5 1 1,5 2 2,5 3 3,5 4 4,5 5
Log population size
Genetic diversity
Figure 4c: Correlation between population size and genetic diversity (sums of euclidian squares/n-1) per population, calculated for Sesleria albicans.
The sums of euclidian squares/n-1 which were taken from the AMOVA calcula-tion and can be used for the measurement of genetic diversity within populacalcula-tions, also were correlated highly significant with the population size (rs=0.7, P<0.001, Figure 4c). In contrast, the correlation between population size and maximum genetic distance was not so strong (rs=0.6, P<0.005).
3.7 Population clustering
In an unrooted and bootstrapped UPGMA dendrogram, based on 344 RAPD markers the 104 individuals of the two species Sesleria albicans and Sesleria caerulea were clearly seperated from each other (Figure 5).
The dendrogram therefore consisted of two major groups. One small group com-prised the individuals of Sesleria caerulea. The other large group consisted of all individuals of Sesleria albicans. The genetic distances between the individuals of the two species were much higher than the genetic distances between the indi-viduals of Sesleria albicans. In this analysis the two closely related Sesleria spe-cies, therefore, showed distinct genetic differences.
Without any exception, all populations of Sesleria albicans and Sesleria caerulea could be discriminated from each other. 16 of 26 populations had bootstrap values which were higher than 80 %. The clustering of these populations, therefore, had considerable reliability. Sesleria albicans showed, however, only a weak cluster-ing of populations accordcluster-ing to their origin from different geographical regions.
The south alpine Eggental population was separated with a high bootstrap value from all populations, which were located in the northern Alps and in central Ger-many. The other populations of Sesleria albicans, however, did not form groups according to their common geographical origin.
Furthermore, the populations from the same habitats did not form independent clusters. Except for the west German grassland populations and the southwest German rocky ridge populations most investigated populations were mixed thor-oughly, without respect to their origin from different habitats.
To investigate whether there is habitat specific clustering within different geo-graphic regions, further cluster analyses were conducted for the populations from southwest (Figure 6) and west Germany only and also no habitat specific popula-tion groups were observed. Even when only the populapopula-tions from the beechfor-ests, rocky ridges, and grasslands on the Swabian Alb were analysed no clustering of the populations from the same habiat could be found.
Sesleria albicans – Results
Figure 5: Bootstrapped cluster analysis (UPGMA) of 104 plants of Sesleria albicans from the Alps (SA, NA) respectively central Europe (CE) and S. caerulea from south Scandinavia (Öla) using 344 RAPD markers, based on the Jaccard‘s similarity coefficient matrix. Plant material of S. albicans was sampled in six different habitats (GR = grass-land, RV = rocky river valley slope, BF = beech forest, LR = lowland rocky ridge, FE = fen, AR = alpine rocky ridge). The cluster analysis showed that the populations were clearly separated but not grouped together according to their origin from the same habitat.
Numbers at the nodes indicate the probability of the branch when the bootstrap analysis was calculated with 1,000 iterations. Population abbreviations follow Table 1.
GR
Figure 6: Bootstrapped cluster analysis (UPGMA) of 56 plants of Sesleria albicans from the Swabian Alb using 344 RAPD markers, based on the Jaccard‘s similarity coefficient matrix. Plant material was sampled in three different habitats (GR = grassland, RR = rocky ridge, BF = beech forest). The cluster analysis showed that the populations were clearly separated but not grouped together according to their origin from the same habitat.
Numbers at the nodes indicate the probability of the branch when the bootstrap analysis was calculated with 1,000 iterations. Population abbreviations follow Table 1.
Sesleria albicans – Discussion
4 Discussion
4.1 Partitioning of molecular variance within and among relict populations